#12068: RULE too complicated to desugar when using constraint synonyms -------------------------------------+------------------------------------- Reporter: crockeea | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.10.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj): This is actually OK in HEAD. We get the RULE {{{ "SPEC bar" [ALWAYS] forall (@ q_a1SJ) ($dQux_a1SK :: Qux q_a1SJ) ($dIntegral_a1U3 :: Integral Int) ($dNum_a1U2 :: Num Int) ($dClass1_a1SM :: Class1 (Foo q_a1SJ Int)). bar @ (Foo q_a1SJ Int) $dClass1_a1SM (T12068.$fClass2Foo @ q_a1SJ @ Int ($dQux_a1SK, $dIntegral_a1U3) $dNum_a1U2) = T12068.bar_$sbar @ q_a1SJ $dQux_a1SK }}} (How likely that rule is to fire in practice isn't clear to me, but perhaps it will.) It works in HEAD because the "silent superclass" story, which adds extra parameters to dfuns, has gone away. c.ff #12074, which is defeated by a `let`. I'm not sure if it's worth adding a regression test. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12068#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler